Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description must carry the full behavioral burden; it does disclose the key trait (mail persists across sessions, retrievable from a different session later). It omits what happens when the same name is armed twice, whether re-arming resets the TTL, and which tool reads the collected mail back, which matters for an asynchronous tool.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two sentences, zero filler, and the persistence property is front-loaded before the usage scenario. Nothing could be cut without losing information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

All three parameters are documented and the tool's asynchronous purpose is explained, so an agent can call it correctly. The remaining gap is the retrieval path: it says to "read the result later from a different session" but never indicates which sibling tool performs that read.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and each of the three parameters carries its own description (including the 60–2592000s TTL range and the 7-day default). The prose adds no parameter meaning beyond the schema, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description pairs a concrete action ("Register a disposable email address") with the defining trait that separates it from siblings: the address "keeps accepting mail after your session ends." That durability trait implicitly distinguishes it from get_email_verification_code and receive_webhook_events, though no sibling is named outright.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It gives an explicit trigger scenario: "Use this when you sign up for a trial or service while your container is alive but need the follow-up email after it recycles." Clear context, but there is no when-not guidance and no named alternative for the case where the container will still be alive.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.